top of page

Eyes

Components covered in this eye section:

  • Orbit

  • Eyeballs

  • Muscles

  • Neurovasculature

  • Lacrimal Apparatus

Orbit

 

Components covered in this orbit subsection:

  • Bones

  • Foramina of the orbit

  • Contents

 

 

Bones

 

7 bone form the orbit:

  • Frontal bone

  • Maxillary bone

  • Zygomatic bone

  • Lacrimal bone

  • Ethmoid bone

  • Palatine bone

  • Sphenoid bone

 

 

 

 

 

 

 

 

 

 

 

 

 

Foramina

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Foramina of the orbit:

  • Optic canal

  • Superior orbital fissure

  • Inferior orbital fissure

 

 

 

 

 

Contents

 

Contents of the orbit:

  1. Intrinsic ocular muscles

  2. Extrinsic ocular muscles

  3. Ligaments supporting the eye

  4. Eyelids & eyeball

  5. The lacrimal (tear) apparatus

  6. Nerves & vasculature

Eyeball

 

Eyeball

  • Outer fibrous layer

    • Cornea (anterior- transparent part)

    • Sclera (posterior- tough opaque part)

  • Middle vascular layer/uvea

    • Choroid 

    • Ciliary body (and ciliary processes)

    • Iris

  • Inner sensory layer

    • Retina

      • Optic non-visual part

 

The eye is divided into:

  • Aqueous humour- watery fluid in anterior segment

  • Vitreous humour- gel in the posterior segment

 

Other structures to note:

  • Lens

  • Anterior chamber

  • Posterior chamber

  • Optic nerve

 

  • Optic disc

  • Central retinal artery

  • Macula

 

 

 

 

 

 

 

 

 

 

 

Muscles

 

Components covered in this muscles subsection:

  • Intrinsic muscles of the eye/Intraocular muscles (IOMs)

  • Extrinsic muscles of the eye/Extraocular muscles (IOMs)

  • Eye movements

 

 

IOMs

 

 

 

 

 

 

 

IOMs:

  • Ciliaris- accomodation (for viewing objects at various distances)

  • Constrictor pupillae- constricts pupil

  • Dilator pupillae- dilates pupil

All have parasympathetic innervation from CN III (occulomotor nerve) except dilator pupillae (sympathetic innervation)

 

 

 

EOMs

 

EOMs:

  • Levator palpebrae superioris

  • Superior oblique

  • Inferior oblique

  • Superior rectus

  • Inferior rectus

  • Medial rectus

  • Lateral rectus

All innervated by CN III (occulomotor nerve) except:

  • Superior oblique- innervated by CN IV (trochlear nerve)

  • Lateral rectus- innervated by CN VI (abducens nerve)

 

 

 

 

 

 

 

 

 

 

 

 

 

Eye Movements

 

Eye movements:

  • Elevation

  • Depression

  • Abduction

  • Adduction

  • Intorsion

  • Extorsion

 

 

 

 

 

 

Remember RADSIN (Recti ADuctors, Superiors INtortors)

 

EOMs:

  • Levator palpebrae superioris (LPS)- elevate superior eyelid

  • Superior oblique (SO)- abduction, intortion, depression

  • Inferior oblique (IO)- abduction, extorsion, elevation

  • Superior rectus (SR)- adduction, intorsion, elevation

  • Inferior rectus (IR)- abduction, extorsion, depression

  • Medial rectus (MR)- adduction

  • Lateral rectus (LR)- abduction

 

 

 

 

 

 

 

 

 

Neurovasculature

 

Arteries

 

Arteries of the orbit and eye:

  • Opthalmic artery (branch of ICA)- passes through optic canal

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Veins

 

Veins of the orbit and eye:

  • Opthalmic veins - passes through superior orbital fissure

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Nerves

 

Nerves of the orbit and eye are cranial nerves:

  • CN II (optic nerve)- passes through optic canal

  • CN III (occulomotor nerve)- innervates ciliaris, constrictor pupillae, LPS, IO, SR, IR, MR (passes through supeiror orbital fissure)

  • CN IV (trochlear nerve)- innervates SO (passes through supeiror orbital fissure)

  • CN V1 (opthalmic nerve)- passes through superior orbital fissure

  • CN VI (abducens nerve)- innervates LR (passes through supeiror orbital fissure)

 

 

Lymphatics

 

There are no lymphatics in the orbit.

Lacrimal Apparatus

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Lacrimal apparatus:

  • Lacrimal gland- innervated by CN VII (facial nerve)

  • Puncta

  • Lacrimal sac

  • Nasolacrimal duct

bottom of page